The inventors herein have recognized a need for an improved system for determining an accurate ohmic resistance value associated with a battery cell. One of the main elements of an equivalent circuit model of a battery cell that is used to represent an electrical response of the battery cell to a flowing electrical current is the DC ohmic resistance value R0 (shown in FIG. 2). Pursuant to Ohm's Law, the voltage drop across the ohmic resistance value R0 is a function of the electrical current through the battery cell multiplied by the ohmic resistance value R0. This voltage drop, and associated i2R power loss, is the power that is unavailable to the intended application of the battery cell. At beginning of life of the battery cell the ohmic resistance value R0 is at a lowest value. However, aging of the battery cell, due to calendar age and electrical current throughput, results in a growing value of the ohmic resistance value R0. Thus, one of the tasks of a battery management system (BMS) is to continuously monitor/estimate the growing value of the ohmic resistance value R0 because of its major impact on the ability of the BMS to deliver power.
Another system does not recognize that an ohmic resistance value associated with an ohmic resistance of a battery cell is dependent on an amount of current flowing through the battery cell. The inventive system determines a more accurate ohmic resistance value by utilizing a 3-D interpolation table having state of charge values, temperature values, current values, and ohmic resistance values.